Porous polymer water filter and methods of use in refrigeration

ABSTRACT

The filtration device of the present invention relies on materials and methodologies that achieve the formation of a structural matrix that may later accommodate the addition of other adsorbent materials as opposed to merely binding adsorbent materials together through the use of compression and/or binder materials. The filter device of the present invention relies on (i) a unique method of processing to achieve maximum density of materials, (ii) a polymeric material having a distinct morphology and (iii) a very small micron diameter of the polymeric material to create uniformity. For example, in place of compression to increase density, the materials comprising the filtration device of the present invention are instead vibrated into a mold cavity. Thus, the methodology of the current invention optimizes how all of the materials comprising the filtration device fit together without compaction. The material being processed is vibrated as it is gradually poured into the mold. Once the mold cavity has been filled to a point where it will hold no more material, it is heated and then cooled. In place of an external binder, the structural material adheres to itself as it softens. This results in a tortuous path matrix of pores rather than an absolute pore barrier.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to filtration devices, novel methods forthe production of the same and methods of use. More specifically, thepresent invention relates to a methodology of vibrating and thensintering polymers having distinct morphologies to achieve a structuralfiltration matrix, which is also capable of accommodating variouscompounds for the removal, reduction or adsorption of undesirablecontaminants in liquids and gases, most notably water and air.

2. Description of the State of Art

The filtration of fluids may be accomplished through a variety oftechnologies, the selection of which is often determined by thecontaminant or contaminants that are being targeted for removal orreduction. Particulates are best removed through a process known asdepth filtration. The filter collects and holds any dirt or sedimentwithin its matrix. Dissolved organic contaminants appearing on amolecular level may be removed through adsorption or, in the case ofminerals and metals, through ion exchange. Very small contaminants,including microorganisms down to sub-micron sizes often require someform of membrane technology in which the pores in the membrane areconfigured to be smaller than the target contaminant; or they can bedeactivated in some manner. Contaminants in drinking water may be brokendown into four groups: (i) turbidity and particulates; (ii) organicbased chemicals and pesticides; (iii) inorganic matter such as dissolvedheavy metals that pose a health risk such as lead; and minerals; (iv)microorganisms such as protozoan parasites, bacteria and viruses. Whilethere is a specific technology for the treatment of each group, somefilters are designed to treat several contaminant groups through asingle filtering technology. Since organic contaminants havehistorically been the most common, activated carbon has been used toremove a wide spectrum of contaminants from liquids, most notablydrinking water. For this and other reasons most prior art fluid filtersare carbon based and commonly known as carbon blocks. The currentinvention relates to an alternative approach to removing contaminantsfrom fluids that provides superior filtration of fluids and otherimprovements over prior art methodologies.

Plastics have long been used for filtering fluids. Such methodsgenerally involve taking plastic pellets and cryogenically grinding theminto a granulated and/or powdered form. This resulting material could beused as produced or it could be screened through a sieve to separate theparticles into more tightly controlled mesh ranges. The plasticparticles are then sintered in a mold. The process, known morespecifically as porous plastics, involves taking the mold filled withthe plastic material up to a temperature where the particles soften butdo not melt, such that all of the particles stick to one another. Themold is then brought back to ambient temperature and the material isejected from the mold. The finished part is at the same time solid andself-supporting while being porous to fluids. Any plastic that can beground into a granular form can be used; and some polyethylene polymersare produced in a powder form. Finer particles create a matrix ofsmaller spaces between the plastic particles which are known as voids orpores. Filtering materials, including but not limited to activatedcarbon, may be added to enhance the filtration of a specificcontaminant. The process of blending into and holding within the matrixof the polymeric material other filtering compounds requires that thetotal surface area of the polymer be greater than the total surface areathat the added materials take up, such that there is sufficientadhesion. When formulated accordingly, the resulting part is durable andself-supporting. Where both the polymeric material and the filtrationcompounds selected generally share a similar bulk density and particlesize the preferred ratio by weight for most filtration applicationsprovides that at least 50% to 60% of the filter by weight be polymericparticles. In this process there is no force, compression nor pressureapplied to the materials before or during processing, such that both thepolymer particles and the filtering materials remain essentially in tact(i.e. they do not lose their original shape). The fluid being filteredflows through the porous matrix where it is forced into contact with theadsorbents or other filtering materials. This filtering technique, knownas tortuous path filtration differs from what is known as absolutefiltration. The size of the median diameter of the pores within theporous plastic filter determine how much of any given contaminant bysize will be allowed to pass through the filter matrix. These porescannot be made to a consistent single size and generally range fromlarge to small, with the filter being measured by its median porediameter (MPD) as determined by a mercury poresimiter analysis. Themedian pore diameter may be manipulated, as stated above, to be largeror smaller by manipulating the size of the particles that comprise it.This includes both the particle sizes of the plastic granules or powdersas well as any material being blended into it.

An alternative method of filter making is known as carbon blocktechnology. Carbon blocks are molded granular activated carbonparticles. The origin came from the need to improve upon the use ofloose bed carbon particles that have been utilized to remove organiccontaminants from water since Roman times. However, loose bed activatedcarbon filters lack performance in specific areas and, as a practicalmatter, take up too much space for many point-of-use applications. Thesedrawbacks led to the development of the carbon block technology duringthe 1980s. Here, carbon particles are blended with a small amount of athermoplastic material, known as the binder, in a general ratio of about4 parts granular activated carbon to 1 part thermoplastic material. Thematerial is thoroughly blended together, poured into a cylinder shapedmold and compressed so as to compact the blended material as much aspossible. The material is then heated to a point where the binder eithersoftens or melts to cause all of the carbon particles to adhere to oneanother. The adhesion process uses only a small amount of binder in aratio to activated carbon granules, which is aided by the compressionthat is applied to the two materials during processing. Once cooled thefinished part takes on the form of a solid cylinder block comprised ofcarbon particles, which is self-supporting while being porous to mostfluids. The cylinders invariably are tube shaped such that there is acore and a wall thickness. Water is directed to flow radially from theoutside diameter (OD) surface of the tube to the inside diameter (ID)and then out one end of the core.

The ability to bond carbon particles together in a fixed bed enablescarbon filters to use finer carbon particles than those traditionallyused in loose bed filtering methods. The use of finer particles in turnincreased the amount of available surface area of the adsorbentactivated carbon, while compression of the particles during processingincreased the density of carbon particles. This density also contributesto increasing the absolute micron rating of the filter since voidsbetween the carbon particles are eliminated, creating an absolutebarrier to the passage of particulates. The Degen and Vanderbilt patents(U.S. Pat. Nos. 4,664,683 and 4,753,728, respectively), both filed in1986, teach the use of binders used in carbon block technology.Vanderbilt disclosed the use of high density polyethylene polymers inlieu of other binders, including the use of an ultra high molecularweight polyethylene (UHMW) polymer specified as GUR 212. In 1991 Koslow,in his U.S. Pat. No. 5,019,311, disclosed an alternative method ofcarbon block manufacture in which the adsorbent activated carbon may beblended with a combination of very low melt temperature binders anddriven through an extrusion tube by an auger. The blended material iscompressed as it is conveyed into the extrusion tube, then heated andquickly cooled to produce an extruded carbon block.

In the filtration of fluids, especially water and air, carbon blockmethodologies have certain limitations which the current inventionovercomes. Carbon blocks are limited to the use of only one primaryfiltering material: activated carbon granules, without which there is nofilter. Further limitations include the lack of depth filtration anddurability. Carbon block filters exhibit a high pressure drop as aresult of the compression used during processing. Fluid filters madeusing the current invention's methodology combined with specificpolymers represent a major departure from prior art filter makingmethods. The current fluid filter invention may incorporate anyfiltering material without reliance on any single material, includingvery fine powders smaller than one micron. Resulting filtersdifferentiate from prior art methods in that they exhibit superiorfiltration performance, excellent depth filtration, a very low pressuredrop, durability, and they may be molded into any shape or dimension.

There is still a need, therefore, for a filtration device wherein thestructural matrix of the filter is independent from the filtrationcompounds, and where the smallest particle size of the filtrationcompounds is unlimited, such that advantage may be taken of the greatersurface area of finer powders. This in turn will allow the filtrationdevice to be formulated to meet a specific task or tasks, while at thesame time exhibiting a number of superior performance features andbenefits over other filter assemblies. There is a further need for afiltration device that is durable, displays enhanced depth filtration,and exhibits minimal pressure drop.

SUMMARY OF THE INVENTION

The filtration device of the present invention relies on materials andmethodologies that achieve the formation of a structural matrix that maylater accommodate the addition of a wide spectrum of filtrationmaterials. The filter of the present invention relies on (i) a uniquemethod of processing to achieve maximum, uniform density of materials,(ii) polymeric materials having an exceptionally small particle sizewith a distinct morphology that is retained throughout and (iii) apolymeric matrix that forms the primary structure of the filter.

The method of processing involves the vigorous vibration of powderedfiltering materials and polymer until they are firmly compacted into agiven space such as a mold cavity. Pockets of air creating unnecessaryvoids between the particles are reduced in this manner. This achievesthe maximum amount of density of materials without external force. Theabsence of force allows both the polymeric material and the filteringcompounds to retain their original shape (morphology) and particle size.The two polymers of the preferred embodiment have distinctly differentmorphologies with each providing different characteristics to theresulting filter.

Thus the morphology of the two principal polymeric materials allows thefilter matrix to be manipulated by adjusting the ratio between the twopolymers, accentuating one attribute over another. The mean particlesize of the polymers further enhances the bonding capability and densityof the filter when blended with filtering compounds, because they have agreater amount of surface area than particles with similar morphologiesbut larger average particle sizes. Also, in this methodology a polymerparticle will typically bond well to any non-polymeric material with amean particle size ranging from very coarse and down to about one halfthe size of the polymer particle. Thus, a smaller polymer particle sizeenables a wider range of filtering materials that can be used with it.Filtering materials in the form of very fine powders exhibit greatersurface area than coarser granules. In fluid filtration one commonobjective is to create a matrix that provides the maximum amount ofavailable surface area of a given contaminant filtering material in thefinished filter.

Unlike alternative methods involving the compression molding of commonfiltration adsorbents with other materials in which a small amount of athermoplastic material binds together a much larger amount of mainlyactivated carbon particles, here the filtering materials are bonded ontoa porous plastic matrix that is equal to or greater in overall surfacearea than the filtration materials being added. In place of an externalbinder whose sole function is limited to the adhesion of the activatedcarbon granules, the polymeric material in the current invention may beformulated to determine such characteristics as structural integrity,median pore diameter of the filter matrix, amount of depth filtration,density of filtering materials and pressure drop. This polymericmaterial in the form of a very fine powder adheres to itself duringprocessing and will not deform when heated.

This combination of vigorous vibration of the structural materials withor without adsorbents and/or other filtering compounds produces a highlycomplex, labyrinthine matrix. This matrix creates a tortuous paththrough which the gas or liquid must flow. Tortuous path, or tortuosity,is an alternative to absolute micron filtration methodologies. Moldedcarbon particle filters, by comparison, are created by compressing alarger mass of coarser particles into a more densely packed matrix andbonding them together with an adhesive material such as a thermoplasticbinder. The matrix of the filter is formed by the filtering materialitself. There are very few pores within this matrix since they have beeneliminated during the compression phase of the processing. Here thelargest of these pores determines the absolute filtering capability inthe removal of particulates. A tortuous path filter may be rated by themedian pore diameter (MPD) within the filter's matrix. The theory ofabsolute micron rating is that any particle larger than the largest poresize in the filter's matrix will be rejected physically. In tortuouspath filtration the particulate passes through a maze ofmulti-directional pores of varying pore diameters in a range that may beboth larger and smaller than the particulate. Randomly, the particulateeventually becomes trapped within a pore that is smaller and isretained, while the liquid or gas being filtered easily passes onthrough. The chances of one particle making it through the labyrinthinematrix are small. There are many advantages to a properly developedtortuous path matrix, one of which is excellent depth filtration.Filters that rely on absolute filtration reject particulates on theexterior surface of the filter, where they accumulate and eventuallyclog the filter. Filters that rely on tortuosity hold particulateswithin the filter matrix, not its surface.

While physical contaminants may be capably removed through tortuous pathfiltration even where the median pore diameter is several times greaterthan the contaminant being retained, dissolved contaminants in gases andliquids can also be removed more effectively. This is due to the currentinvention's ability to utilize powdered materials that heretofore havebeen regarded as too fine. For example, a single gram of carbon may beactivated to have a total surface area of up to 1500 m². The more finelyit is ground the more of this surface area becomes available. Availablesurface area may be defined as that amount of material that isphysically exposed to the fluid being filtered. Prior art attemptsutilize fine powders has made only moderate progress and has fallenshort of the achievements of the current invention, where there is nodownward limitation to the particle size of the filtering materials.

Additional objects, advantages, and novel features of this inventionshall be set forth in part in the description and examples that follow,and in part will become apparent to those skilled in the art uponexamination of the following or may be learned by the practice of theinvention. The objects and the advantages of the invention may berealized and attained by means of the instrumentalities and incombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specifications, illustrate the preferred embodiments of the presentinvention, and together with the description serve to explain theprinciples of the invention.

In the Drawings:

FIG. 1 is a photomicrograph demonstrating the morphology of the firstbase polymeric material, referred to as PMX CF-1.

FIG. 2 is a photomicrograph demonstrating the morphology of the secondpolymeric material, referred to as PMX CF-2.

FIG. 3 is a graph of the particle distribution of the base materialshown in FIG. 1 demonstrating that the average micron diameter isapproximately 37 microns.

FIG. 4 is a graph of the particle distribution of the material shown inFIG. 2 demonstrating that the average micron diameter is approximately60 microns.

FIG. 5 is a graph of a laser particle analysis of the particledistribution density of filtering adsorbent material used in one of thepreferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The filtration device of the present invention relies on (i) a uniquemethod of processing to achieve maximum density of materials withuniform particle distribution, (ii) a combination of polymeric materialshaving distinctly different morphologies to create a formed, structuralfiltration matrix and (iii) a polymeric material having a very smallmicron diameter that enhances the use of finely powdered filteringcompounds. These compounds may include adsorbents, such as but notlimited to granular and powdered activated carbon, metal ion exchangezeolite sorbents such as Engelhard's ATS, activated aluminas such asSelecto Scientific's Alusil, ion exchange resins, silver, zinc andhalogen based antimicrobial compounds, acid gas adsorbents, arsenicreduction materials, iodinated resins, textile fibers, as well as otherpolyethylene polymers. The formation of a structural filtration matrixaccommodates the presence of filtering compounds, which may beformulated to a specific task such as targeting one contaminant only orone group of contaminants, such as for example heavy metals; or it maybe formulated to filter out a broad spectrum of contaminants fromvarious contaminant groups. The ability to incorporate any filteringmaterial of any particle size or any combination thereof into thepolymeric matrix enables greater flexibility in formulating a filter toa given task.

The method of the present invention utilizes vibration rather thancompression of the materials to be sintered. Vibration optimizes how allof the materials fill the mold completely without force or deformationof the particles. The mold receiving the material being processed istherefore vibrated as the blended material is gradually conveyed intothe mold. Once the mold cavity or cavities has been vibrated to a pointwhere it will hold no more material, it is free sintered such that it isheated to a point where all of the polymeric materials soften on thesurface and stick to the surrounding particles and is then returned toambient temperature. The base polymeric materials comprising the filtermatrix of the present invention are two very fine polymer powders in the30 to 60 mean particle size range, respectively, which become tacky atelevated temperatures yet without losing their distinct morphologies.This causes the particles to adhere permanently to one another duringsintering, as well as forming a surface bond to any filtering materialsthat have been added. This is characteristic of very high and ultra highmolecular weight polymers, of which the latter of more preferable. Oncethe material is cooled, the finished part, which is now self-supporting,exhibits a complex internal matrix comprised of millions of minute,interconnected, multi-directional pores of varying diameters forming atortuous path obstacle to the through flow of contaminants in fluids.The filter may be formed using only one or both of the polymer powders,and may include any filtering material that remains stable at theprocessing temperature of from about 275 F. to 375 F. When finelypowdered filtering compounds are used, the interior surfaces of theplastic matrix pathways become coated with the finer powders offiltering material that are smaller than the polymer particles. Therelatively coarser particles of filtering material fill in the porevolumes created by the minute void spaces. This combination creates evenfurther tortuosity and reduces the median pore diameter of the filtermatrix as well.

These polymers are specifically characterized, for the purpose andresulting success of the current invention, as follows: (i) they eachhave individual morphologies that contribute to the surface area,durability, density and tortuosity of the filter's matrix; (ii) theywill soften and adhere to each other or to other materials when heatedto a critical temperature; (iii) during processing they retain theirrespective morphologies; and (iv) their respective micron diameters arecritical to the enabling of the use of the materials in the preferredembodiments. For example, PMX CF-1 (FIG. 1) has a unique morphology,much like popcorn, in which the surface is convoluted and the particleitself is perforated, and a bulk density of 0.25 to 0.30 g/cm³. Thisunique morphology provides a considerable increase in surface area ofthe particle as compared to PMX CF-2 (FIG. 2), which has a traditional,spherical shape and a bulk density of 0.40 to 0.48 g/cm³. Eachparticle's morphology provides a different characteristic, as does itsbulk density and average particle size. For example, PMX CF-1's expandedsurface area and irregular shape creates a very strong, somewhatelastic, durable part when processed according to the methodologydisclosed herein. The polymer itself is vented such that fluids flowboth through and around it. It easily bonds to very fine powders thatare comparable to or smaller in particle size to itself; but it willalso bond well to much larger particles where necessary. Where the PMXCF-1 material provides outstanding strength, the PMX CF-2 material'smain attributes are greater density of materials and an elevatedpressure drop. A filter made solely of PMX CF-2 and filtering materialsrequires a ratio of more polymer-to-filtering material, generally in aratio of about 3:2 by weight, since PMX CF-2 has less surface area. Asmore material is added the resulting part becomes weaker. This weaknessis a result of the polymer's spherical morphology, since spheres providefewer points of contact for adhesion in comparison to the irregularshaped particles of PMX CF-1. In the process of developing a superiorfluid filter, the two PMX materials, each with their respective particlesizes and opposing morphologies, are blended in differing ratios to oneanother and other filtering materials to achieve a finished filter partthat acquires qualities of both polymeric materials. The method of thepresent invention also teaches the benefits and superiority of creatinga polymeric filter matrix from the two PMX polymers, whose morphologyand size enable finer, powdered adsorbent materials to be used toenhance performance. The durability and elasticity gained by using PMXCF-1, combined with the increased density created by using PMX CF-2,enable a variety of formulations to be created that accommodate a widerrange of filtering compounds used in removing contaminants from liquidsand gases. The ones selected for the preferred embodiment are PMX CF-1and PMX CF-2, manufactured by Ticona, a division of Celanese, located at90 Morris Avenue, Summit, N.J. 07901, USA. However, polymers availablefrom other manufacturers of very high and ultra high molecular weightpolymers that are comparable in particle size, bulk density, morphologyand a molecular weight of from about 750,000 to 3,000,000 may also beused.

While the two polymers have the same melt flow characteristics, the twoPMX polymer particles differ from each other in morphology, bulk densityand average micron size. The morphologies have been shown in FIGS. 1 and2, while the particle size distributions are shown in FIGS. 3 and 4. InFIG. 3, PMX CF-1 is shown to have an average micron diameter of about 30to 40 microns, with a total range from 10 microns to 100 microns. InFIG. 4, PMX CF-2 is shown to have an average micron diameter of 55 to 65microns, with a particle distribution range from 10 to 180 microns.However, the PMX CF-2 powder may be screened through a sieve so that itsaverage micron diameter is adjusted down to about 30 to 40 microns.Alternatively, instead of sieving the material, any commerciallyavailable polymer of similar characteristics with the desired micronsize and morphology would suffice. The morphology is significant sincePMX CF-1 exhibits a greater amount of surface area, a very small microndiameter and an irregular shape. The unusually small micron sizecombined with the particle's unique shape as shown in FIG. 1 allow thepolymer particle to bond more thoroughly to other particles duringprocessing since there are more contact points than a typical sphericalshaped polymer particle, such as the PMX CF-2, as shown in FIG. 2material. The expanded surface area enables the particle to accommodatemore finely powdered filtering compounds that bond to it duringprocessing. Finally, the small micron size adapts more easily to othermaterials of any particle size or distribution range, but especiallywell to particles of a similar size or smaller. Smaller particles becometrapped within the irregular surface of the PMX CF-1 polymer particleitself without decreasing its ability to adhere to other adsorbentmaterials during processing. This characteristic is specific to only PMXCF-1. This is advantageous since, as a rule, the finer an adsorbentmaterial is powdered the better it will perform in filtration since moreof its surface area is exposed to passing contaminants. Onecharacteristic of the PMX CF-1 polymer is that when it is blended withgranular or powdered additives such as the aforementioned compoundsand/or adsorbents, it is very durable with lesser density and thehighest amount of depth filtration capability. Depth filtration is theability to trap and hold suspended particulates from a fluid stream. AsPMX CF-2 is formulated into the material, the parts gain density withgreater part weight, while the pressure drop increases slightly. Theincreased pressure drop does not actually denote a smaller median poresize; rather, it results from the replacement of the CF-1 material,which is itself porous to fluids, by the CF-2 polymer, whose sphericalshape is non-porous. As fluids flow through the filter matrix the CF-2material has reduced the total pore volume within the matrix. Bybalancing these opposing qualities of the two polymers a filter may beformulated to achieve very specific goals. For example, where a fluidcontains both particulates and contaminated with dissolved organics suchas for example, an unacceptable level of pesticidal residue, theobjective may be depth filtration in conjunction with an adsorbent suchas activated carbon. Here the solution might be a filter comprisingabout 50% PMX CF-1 and 50% finely powdered activated carbon particlessuch as those shown in FIG. 5, or a more coarse, granular activatedcarbon particle size ranging from about 45 to 180 microns. The filtermay be made to have greater density by replacing some of the CF-1 withCF-2. In this case the over all filter weight increases. The actualratio between the two polymers would subsequently be determined by thedesired flow rate of the fluid being filtered and the actual geometry ofthe filter part when molded. However, once a formula has beenestablished the process may be repeated continuously with predictablefilter performance so long as the added filtering materials remainwithin certain tolerances such as mean particle size, particledistribution density, bulk density and moisture content. The mostimportant of these is mean particle size and distribution density, whichmay quickly be determined before processing through a laser particleanalysis such as the one shown in FIG. 5.

An important factor in the performance of any compound or adsorbent suchas activated carbon to filter dissolved contaminants from a through flowof a gas or liquid is (i) how much of the original surface area of thecompound or adsorbent material has been retained (not lost) duringprocessing, and (ii) how to maximize the amount of available surfacearea that is directly exposed to the contaminated fluid stream. Priorart methods of fluid filtration have been based on methodologies andmaterials that blind off portions of the total available surface area ofa filtering compound. Blinding simply means that an exchange site on thesurface of a filtering material such as an adsorbent or an ion exchangematerial is interrupted by a particle of binder such that it does notcome into contact with the fluid stream. Where compression is used thefiltering materials are forcibly imbedded into the binding materialunder heat and pressure. Such binders deform under pressure, lose theirmorphology and blind off a portion of the filtering material. Very lowmelt temperature binders simply liquefy and absorb very fine powders andblind larger particles, reducing the amount of available surface area.In the method of the current invention very fine powders bond to themassive surface created by the polymeric structural filtration matrix.Where exceptional filtration of dissolved organics and metals in aliquid such as water is desirable, the use of such finely pulverizedfiltering compounds is an important achievement because they exhibitmore available surface area, which in turn increases the contact timebetween the filtering material and the contaminant.

The novelty of the filter of the present invention relies upon theformulation, interrelationship and use of the two polymers as depictedin FIG. 1 and in FIG. 2 when processed using the aforementionedvibration/sintering method. When used alone each polymer creates afilter with certain characteristics that differ from each other. Bycombining the two polymers in a given formulation with or without theaddition of filtering materials, the finished filter takes on attributesof both polymers. This novel relationship in conjunction with theprocess methods is capable of producing fluid filters that are superiorin performance while eliminating numerous disadvantages associates withprior art filter making methods. Each of these improvements will bediscussed in detail but may be summarized as follows: (1) superioradsorption of dissolved organic contaminants and/or metal ion exchangewhen combined with the appropriate filtering compounds; (2) ability toaccommodate any filter material or combination of filtering compounds ofany particle size ranging from under one micron; (3) the filters may bemolded into any shape with a wall thickness down to 0.100″; (4)exceptional durability such that the finished filter will not crack,splinter or fracture on impact; (5) the pressure drop may be decreasedor increased depending upon the formulation with the advantage of beingcapable of superior filtration without a significant loss in pressure asmeasured directly before and directly after the filter; (6) the filterexhibits exceptional depth filtration which enables it to continuefiltering dissolved organic and inorganic contaminants without prematureclogging due to the presence of particulates in the fluid stream.

Most applications in filtering fluids require the use of specificfiltering compounds. The most common is activated carbon. Known as anadsorbent, activated carbon will take up and hold on its surfacedissolved organic contaminants such as pesticidal residues, organicvapors, etc. It will also eliminate chlorine in drinking water in aprocess known as reduction. Other filtering materials work on theprinciple of ion exchange. For example, heavy metals such as lead may beremoved from drinking water using a metal ion exchange zeolite sorbentsor activated aluminas. Yet other filtering materials includeantimicrobials. These are typically silver or halogen based productsthat discourage the growth of bacteria and other microorganisms.Filtering compounds that are commonly used in filtering gases andliquids are available in powder form and a partial listing of filteringcompounds that may be used in the present invention are listed below inTable I.

TABLE I MATERIALS FUNCTION SUPPLIERS ACTIVATED CARBON ORGANICS BARNEBYSUTCLIFF REMOVAL/DESICCANT ACTIVATED CARBON ORGANICS CARBON RESOURCESREMOVAL/DESICCANT ATS (METAL ION EXCHANGER) HEAVY METALS REDUCTIONENGELHARD MINERALS ALUSIL (ACTIVATED LEAD REDUCTION SELECTO SCIENTIFICALUMINA KDF HEAVY METAL REMOVAL KDF FLUID TREATMENT, INC., AQUABINDARSENIC REMOVAL APYRON TECHNOLOGIES AGION (SILVER ANTIBACTERIAL AGIONTECHNOLOGIES ZEOLITE) IODINATED RESINS BACTERICIDE PENTAPURE, INC. FLOCKPARTICULATE REMOVAL CLAREMONT FLOCK POTASSIUM ACID GAS ADSORPTION IONEXC CHEM CARBONATE CALCIUM CARBONATE ACID GAS ADSORPTION IONEX C CHEMPOTASSIUM IODIDE ACID GAS ADSORPTION IONEX C CHEM POTASSIUM HYDROXIDEACID GAS ADSORPTION IONEX C CHEM ION EXCHANGE RESINS CONTAMINANTREDUCTION SYBRON CHEMICALS PMX CF-1 FILTER MATRIX TICONA PMX CF-2 FILTERMATRIX TICONA

How the above materials may be used to create superior filtration offluids relies on a method of processing that accomplishes two things:(1) the average particle size of the filtering material determines howmuch of its available surface area comes into contact with the fluidbeing filtered, such that the smaller the particle the greater theavailable surface area. For example, it has been noted that 1 gram ofactivated carbon is capable of having up to 1500 m² of surface area.Activated carbon is available in granular form or it may be pulverized.Using the method and materials of the current invention, particles ofactivated carbon with a mean particle diameter of only 22 microns may beused. What is more the chart below demonstrates that 90% of the actualparticle distribution ranges from <1 micron to 45 microns. While the useof particles as small as only 22 microns on average and the ability toaccept particles down to sub-micron sizes has been demonstrated,preserving the available surface area is an important attribute to thisinvention. Most filter making technologies in the prior art rely ondensity of materials. Compression is used to maximize the amount offiltering material and to compensate for what is typically only arelatively small amount of thermoplastic binder. This method requiresfiltering materials with larger mean particle sizes and a cut off pointbelow which particles simply cannot be used. In the current inventionthe typical filter contains 50% or more polymeric material in the formof one or both of the PMX CF-1 and PMX CF-2 polymers. Because of thisthe total surface area for bonding is greater and the particle size ofCF-1 material combined with its unique morphology creates a massivelygreater surface area than traditional morphologies. The CF-2 polymer'sspherical morphology is unique because of its average size of only 60microns, which gives it greater surface area.

While one of the preferred embodiments calls for a powdered activatedcarbon as referenced above and further evidenced by a laser particleanalysis seen on Table II, there are other carbon particle distributionswhich are used to create different features. Where the objective is tooptimize the filtration of dissolved organic based contaminants, thegreater amount of available surface area found in powdered activatedcarbon yields superior results. However, coarser mesh carbons rangingfrom 45 to 180 microns render a more rounded filter, which performs verywell with a more open pore structure that has greater depth filtrationand only a very modest pressure drop. Also, the most common filteringmaterials for heavy metal removal are very fine powders which take uplarge amounts of surface area of the chosen polymers. To compensate forthis take up and where activated carbon is also required, a particlesize range of 45 to 180 microns can be preferable because the largerparticles of activated carbon take up less surface area of polymer,thereby balancing the formula so that the filter adequately removes bothheavy metals and dissolved organic contaminants.

TABLE II Laser Particle Analysis of Powdered Activated Carbon in aPreferred Embodiment Calculations from 0.375 μm to 948.3 μm Volume: 100%Mean: 21.86 μm Median: 15.65 μm D(3,2): 6.736 μm Mode: 19.76 μm S.D.:23.83 μm C.V.: 109% Skewness: 3.472 Right skewed Kurtosis: 17.36Leptokurtic

TABLE III Particle Distribution Density from Table II %< 10 25 50 75 90μm 3.237 7.354 15.65 28.94 43.99

In still other applications some filtering materials are available onlyin highly coarse particle sizes. Activated carbon, for example, isreadily available in micron size ranges starting at 1000 microns andlower and these may be used in combination with the PMX CF-1 and PMXCF-2 polymers to create a very open pore structure with good depthfiltration and moderate reduction of organics, such as in pre-filtrationapplications. Non carbonaceous materials very often are not available inpowder from. In such instances the PMX CF-1 and PMX CF-2 polymers willaccommodate particles as large as 1000 microns. One particular instanceof this is where KDF, a fluid treatment compound comprised of zinc andcopper is commonly used for the removal of heavy metals and chlorine.KDF is made of relatively coarse metallic particles, which bond verywell to the PMX CF-1 and PMX CF-2 polymers, with the former performingespecially well due to its superior bonding capability and flow throughcharacteristics.

While the respective morphologies of these two polymers is important inthe development of a filter with unique characteristics, their micronsize and particle distribution enables the filter to accommodate bothgranular as well as finely powdered compounds of similar or smallermedian particle diameters. The objective is to create a very highperformance finished filter that is durable, exhibits good depthfiltration, has adequate density of materials to give it greatercapacity, and an acceptable pressure drop.

The PMX CF-1 material exhibits greater surface area, superior bondingcapability, and is highly durable with a relatively slight pressuredrop. A filter made with PMX CF-1 provides the maximum amount of depthfiltration and tortuosity when formed by itself or in conjunction withfiltering materials. The PMX CF-2 material with its spherical morphologycreates a denser matrix such that more material fills the same amount ofspace. This creates a higher pressure drop as compared to PMX CF-1. Aseither of the polymers is added to the other the finished part takes onattributes of both such that an ideal formula may be achieved.

A starting point in the development of a formula is generally a filterwhich contains about equal amounts of each polymer, which is thenblended with from about 0.025% up to 55% by weight of the chosenfiltering material. Certain variables control the actual formula. Forexample, the finer the filtering material to be added, the greatersurface area of polymer will be required since finer particles cover agreater surface. The geometry of the part may be delicate or it may bestrong. For example, a part with a wall thickness of 0. 125″ requiresthe strength of the polymeric material to be self supporting, while apart with a wall thickness of 0.500″ becomes self supporting with lesspolymeric material content. Also, delicate parts favor a greater amountof PMX CF-1 due to its durability, whereas strong parts may only requirea lesser amount of PMX CF-1 and can be primarily made of PMX CF-2. Theadded filtering material may be as small as 0.025% by weight of thetotal part up to 55% by weight, which will depend on the filteringobjective.

The part may be comprised of only one of the two polymers, or a blend ofthe two in which the ratio may be any given amount of one to the other.This wide spectrum of possibilities in formulations allows the filter tobe formulated to the particular characteristics of the materials. Thisis significant because various filtering materials available in powderform will vary in mean particle size, particle distribution density, andbulk density. To rely on only one formula would limit the fullutilization of filtering materials. The use of adsorbent materials suchas activated carbon with a coarser particle distribution is lessefficacious in the removal of dissolved organic contaminants. Suchcoarser materials open up the median pore diameter and provide lesssurface area to be exposed to the liquid or gas flowing through thefilter's matrix. Yet there are filtration applications where a coarserparticle distribution may be advantageous. For example, filters whosematrices are configured in this manner exhibit a very low pressure dropand exceptional depth filtration. In such formulations the startingpoint may be a blend of polymers to filtering material where the polymeris PMX CF-1 by itself in a ratio of 1 part polymer to 3 or 4 partsgranular activated carbon. The PMX CF-1 in this instance gives the finalpart sufficient strength and durability to be self supporting as aresult of its greater adhesion characteristics. Here the reduced surfacearea of the filtering material permits a reduced amount of PMX CF-1 usedto mold the part together. It should be noted, however, that suchfinished parts are marginally self supporting and must be reinforcedwith the structure of an outer container or more PMX CF-1 must be useduntil the right balance has been achieved. There are many applicationswhere depth filtration and low pressure drop are important. One examplewould be a water filter used to filter water stored on a roof tank as inmany Latin American and Asian countries. The water is physically dirtyand the gravity water pressure is factored by the vertical distancebetween the tank and the outlet. The ideal solution in this instance isa filter which will not clog and flows easily with minimal pressure.

Apart from such applications as noted above, a perfectly uniform matrixis most desirable for even filtration; this is best achieved bymaintaining uniformity in the particles sizes being processed. Where thepolymer particle is itself a fine powder, and where it processesuniformly with equally fine powders, the finished filter will have auniform filter matrix while exposing the largest amount of surface area.This explains why the unusually small particle size of the PMX polymerparticles plays a key part in the invention's novelty. A larger polymerparticle with a similar morphology has less surface area and processespoorly with finer powders.

The next step is the exact method of processing. Once a formula has beenestablished to exhibit the desired characteristics in the finishedfilter, it must be processed in a specific manner. The materialsselected are blended together so that the final material is homogeneousand free of clumps. A ribbon blender or the like is generally capable ofaccomplishing this. The blended material is then conveyed from theblender to a mold that may have one or more cavities in the mold. Thecavity geometry will determine the final shape of the finished part.This form may be any given shape including a square or rectangular cube,a disk, a flat panel, a cup, a rod or a cylinder that is solid or acylinder that has a core, being open at only one end or open at bothends. The material can also be formed into a continuous sheet materialwith a thickness down to 1 mm. The only limitation to the shape of thepart is that it be able to be removed from the mold after processing.

As the basic material blend is conveyed into the mold cavity the mold issimultaneously vibrated using any standard mechanical industrialvibrator available. Commercially available vibrators will shake in an upand down motion or they will swirl the material as they vibrate, orboth. The degree of vibration may be increased or decreased depending onany number of variables including the overall mass of the mold byweight, the size of the finished filter parts, as well as the aspectratio of the parts where the length is greater than the width. Vibrationshould begin before the powder is conveyed into the cavity or whereparticles may migrate away from each other and separate in the mold,vibration may be commenced after the cavity begins to fill up with thematerial. In some applications, learned through experimentation, novibration may be required. Shorter and longer vibration cycles yielddiffering results, which are even further differentiated by thecharacteristics of the cavities depth and width. The objective ofvibration is two-fold: (1) to gently rid the powdered materials of airpockets causing void spaces between particles without disrupting orcrushing the particles being vibrated; and (2) to maximize the amount oftotal powder that will compact into the mold cavity without force orcompression by causing them to shift and rotate until they fit togetherwith other particles. A shorter vibration cycle may cause lesscompaction while greater vibration may cause unwanted particleseparation where finer particles migrate away from larger particles.This problem is of particular concern where the polymeric material isprimarily spherical. Abandoning the vibration of the material prior tocompletely filling the mold is unadvisable since the last material addedmay have a different particle density; over vibration will eventuallycause different material particles to migrate away from each other.There are exceptions, such as when it is not desirable to have maximumdensity of material, or where there is a significant difference in theparticle sizes, as will be explained below.

At the end of the vibration cycle, the mold must be covered with a coverplate and is heated to a temperature such that the polymers will becomesticky enough to adhere to other polymer particles or a combination ofother polymer particles and filtering compounds. While PMX CF-1 and PMXCF-2, in the preferred embodiment, have a molecular weight of about3,000,000 and will not lose their original morphology if heated beyondtheir softening point, lower molecular weight polymers in the 750,000and higher range and with similar morphologies may be heated to asoftening point and used as well. Where such polymers are used verytight controls on the temperature of the mold during sintering must beestablished to avoid deforming or melting the polymer. It is for thisreason that ultra high molecular weight polyethylene polymers arepreferable for their ease of processing. Once it has attained thenecessary temperature, usually from about 225 degrees F. to 375 degreesF. or higher, depending on the specific melt flow index of the polymer,the mold is allowed to cool back down to ambient temperature. Thecooling cycle may be natural or assisted by any form of cooling and theamount of time to cool is irrelevant to the quality of the finishedpart. Once the mold has been cooled the powdered materials are formedinto a self-supporting porous filter. It will allow any gas or liquid toeasily flow through it. If it is entirely made of polymer, it will havefilter characteristics that screen out physical contaminants or it mayalso be used to disperse a gas into minute bubbles. It can also beformulated to remove larger parasites such as Giardia and otherprotozoans. In water filtration, for example, there are specificapplications where it is desirable to remove such microorganisms withoutthe use of activated carbons, which are known to breed bacteria.

As discussed above, the performance of the filter to remove a specificcontaminant will depend on the filtering compound chosen. Activatedcarbon is recognized as an adsorbent of organic based contaminantsranging from dissolved organic matter to chemicals and pesticides.Certain titanium metal ion exchange zeolites such as Engelhard Mineral'sATS™ Sorbent, and activated aluminas such as Selecto Scientific'sAlusil™ have been developed to remove lead and heavy metals from aliquid such as drinking water. Silver ions are known to inhibit thegrowth of pathogens such as E. coli bacteria and are available in avariety of forms that include synthetic zeolites where the sodium ionshave been exchanged for silver and zinc ions. One such popular syntheticzeolite is Agion™, manufactured in Japan by Sinanen and distributed byAgion Technologies. Certain rules determine more desirable results. Mostnotable is the relationship between the total surface area of thepolymer matrix and the amount of surface area taken up by the filteringcompound that bond to the matrix during processing. A consistentlydurable, finished part will be formulated such that there is alwaysgreater surface area of polymer to filtering compound. Whereas inprocessing the relationship amongst ingredients may be proportioned byweight, relationships must be first formulated by volume of surface areawith respect to each other and then converted to weight for convenience.If the total surface area of filtering compound exceeds the totalsurface area of the polymer(s), the part will begin to exhibit loss ofstructural integrity and durability. Therefore the polymer used in thepreferred embodiment should always be greater in surface area by asufficient margin.

The polymeric matrix of the filter provides physical structure,tortuosity and a surface area onto which filtering materials may bebonded. It is the supporting skeleton of the filter. If the addedfiltering material does not take up more polymeric surface area than isavailable the finished part will become self-supporting. A powderedmaterial of any particle size may be added, or a material with aparticle distribution range that includes sub-micron size particles maybe successfully employed. However, a small amount of very fine powdersunder 5 microns will quickly coat the entire surface of the polymermatrix and will thus limit the total amount that can be used withoutloss of structure. In the formulation stage, particles of polymer andfiltering compounds of equal size and general bulk density may as a ruleare blended in equal amounts by weight where at least 10% or more of thetotal polymeric material is PMX CF-1. Filtering compounds that aresmaller in particle size than the basic polymer material are not onlyaccommodated by the greater surface area of PMX CF-1 because of thepolymer size, but the unusual morphology takes this concept to an evenhigher level of performance. (See FIG. 1.) Another feature of the PMXCF-1 material is that it is vented with microscopic channels that coursethrough the interior of the particle. This feature further enhances theflow through characteristics of the filter, including a reduced pressuredrop. The unique morphology of PMX CF-1 allows very fine particles offiltering material to bond to the surface of the larger polymerparticles, while filtering compounds that are equal to or larger thanthe polymer become trapped within the pores or void spaces of the filtermatrix. In this way the non-polymeric compound is integral to thefiltering but not to the structure.

Special Characteristics

The aforementioned process of sintering chosen structural materials suchas PMX polymers CF-1 and CF-2 with added compounds enables filters toexhibit a number of qualities that differentiate the invention fromprior art. These may be summarized as follows:

Impact resistance. Since the filters are comprised of from about 50% to100% of a basic material comprised of the PMX material formulations asdescribed above, they are durable and resist cracking or breaking onimpact. Wherever a filter must be unbreakable, such as portableapplications in the wilderness or military uses, the filters may beformulated to achieve that specific goal while still achieving superiorfiltration.

Pressure Drop, or Delta P, is the variation in water pressure before anddirectly after passing through a given filter. The drop is determined bysubtracting the latter from the former such that if the pressure goinginto the filter is 60 psi and then 50 psi coming out, the pressure dropis 10 psi; and so on. Pressure drop is unavoidable. However, a filterdemonstrating the least amount of pressure drop without correspondingloss of performance is preferable. This advantage in the currentinvention is owing to the internal filter matrix that contains more flowthrough channels than a compressed filter. The greater number ofchannels is a result of the polymer characteristics combined with thealternative method of processing. Filters using absolute micronfiltration exhibit corresponding increases in pressure drop as thediameter of the pores decreases. Therefore a superior method offiltration is through tortuosity. The number of pathways through a givenfilter matrix is greater than a similar filter created through thecompression of particles together, especially where the compression isin the range of 30%. This was further proven out by comparing filtersusing PMX CF-1 with and without PMX CF-2. A filter using 100% PMX CF-1was tested for air permeability against filters in which PMX CF-2 wasblended. The first blend was 90% PMX CF-1 to 10% PMX CF-2. The pressuredrop increased slightly. However, at 80% PMX CF-1 to 20% PMX CF-2 therewas a distinct and measurable increase in pressure drop. This increasecontinued as the ratio was subsequently changed to 70% to 30% down to60% to 40%. Since there were no other changes or variables, the changemust be traced back to the polymer formulations. Thus pressure drop maybe modified according to the application through the relationshipbetween the PMX CF-1 and CF-2. The importance of particle size impactsthe characteristics of the filter. Where the CF-2 material is sieved tomimic the particle size and distribution density of the CF-1 material,the finished part displayed less density and a lower pressure drop.

Depth Filtration. Absolute micron rated filters have little or no depthfiltration capability, especially where the absolute micron rating is inthe 1 to 10 micron range. To achieve, for example, a 1 micron absolutepore diameter all pores larger have been eliminated. This in turn causesthe filter to reject any particle or microorganism larger than 1 micron.In a flow through pattern these particles are rejected at the surface ofthe filter. Depth filtration is in fact enhanced by the tortuous pathmethod since it does not rely on absolute pore size. Filters of thecurrent invention exhibit a considerably larger number of pores with amedian pore diameter significantly larger that the particles it iscapable of filtering. Commercially, a filter with depth filtration ispreferable since filters are distributed throughout the country or worldwith knowing what amount of suspended solids may be in the unfilteredwater. Most water has fine sediment that can prematurely clog a filterby collecting on its surface. Where a filter is configured to rejectparticles of a given size and larger, as in absolute filtration, thesurface of the filter does not permit any particle larger than x (wherex=the micron rating) to enter the filter matrix. The benefit to tortuouspath filtration with its accompanying depth filtration capability isthat it filters within the matrix rather than on the filter's surface,thus avoiding premature clogging.

Molding capability is another valuable attribute of the invention. Here,the durability allows parts to be shaped into any form. In liquidfiltration, today most methods relying on prior art are manufacturedsolely in the form of a cylinder shaped filter in which the liquid isdirected to flow in radial direction from the outside diameter of thecylinder into the inside diameter of the cylinder, passing through awall thickness of bound carbon particles. The cylinder shape of theparts is limiting, as well as the other limiting feature that thefinished parts will splinter and crack easily. Here, the inventionprovides for parts that are made of a durable plastic which may beformed into any shape, even with all thickness down to about 3000microns where adsorbent are used. The parts may be formed into disks,rods, cups, cylinders or closed end cylinders. The availability of theforms expands product development potential where the finished filteringdevice is not bound to a cylindrical filter shape. Cylinders that aretubes, open at both ends, may be closed at one end during processingrather than having to be closed off with an end cap. This reduces insome applications manufacturing costs and increases speed of assembly ofthe filter into a finished device or housing. In air filtration, mostfilters such as for Organic Vapor (OV) adsorption, or OV masks, areconstructed of loose granular activated carbon particles in the generalrange of 250 microns and larger. These are packed tightly into acanister and air is drawn through them to filter out organic vapors. Noprior art applications have been able to reach the demands of airfiltration without using an external source of pressure because thepressure drop is too high. In a respirator such as an OV mask only one'sbreath is used to draw in the air through the carbon.

Still another application that relies on this special molding capabilityis in the adsorption of organic vapors combined with humidityregulation. Activated carbon is an excellent regulator of humidity. Thehigher the activity of the carbon the better it will absorb moisturefrom a gas such as air. High activity activated carbons such as thosehaving a Carbon Tetrachloride Number (CTC #) of +95 are most preferablewhere very high performance in is a must. However, even standard carbonswith a CTC number of +65 are more than adequate for most filtrationapplications.

Low humidity levels below a relative humidity (RH) of 40 will allow thehumidity to pass over a bed of activated carbon without reduction. Asthe humidity increases over 40 RH, the humidity is removed from thepassing air. This quality of activated carbon has been adapted and usedin regulating the RH in delicate instruments. One application inparticular is controlling the both organic vapors and RH inside of acomputer disk drive, which is vulnerable to both. Thus one filter iscapable of removing trace amounts of organic gases from incoming air,while maintaining humidity levels that are either not too high or nottoo low. The presence of very minute amounts of acid gases, for example,has proven to corrode the heads on computer disk drives, as hasexcessive humidity levels.

Higher performance: The use of finely powdered adsorbents such asactivated carbon powders, zeolites, activated aluminas, antimicrobials,etc. in the current invention perform at a higher level because thefilter structure optimizes the interface between the adsorbent compoundsin powder form and the contaminants being filtered out of the gas orliquid. This is especially true of activated carbons, which are one ofthe leading materials used in filtering air and water. Powderedactivated carbon with a mean particle diameter of 22 microns (see FIG.5) is optimal because it has the greatest amount of available surfacearea. However, it has never before been used as a primary filteringmaterial for fluids because in most processes it is too fine to behandled or formed. In the process plus material of the currentinvention, fine powders are actually preferable as they create a betterfinished filter matrix. In water filtration, the removal of suchcontaminants as MTBE, a gasoline additive used today in place of lead,as well as Volatile Organic Chemicals (VOCs) is preferable but noteasily attainable with conventional filtration methods.

Economical benefits of the current invention give it a price advantageover other processing methods for making water filters. The ability toutilize fine powders without loss of surface area enables filters to bemade with less material. This is usually in a range of 65% to 50% lessmaterial to achieve equal performance to filters using the prior art. Toestablish this feature, the following comparative test was performed:Two water filters were tested, each with the ability to reduce >99% oflead in drinking water. Filter A was taken from a commercially availablesource. The manufacturer determined that given the factors of flow andcapacity that 18% of the filter by weight was Engelhard's ATS. Thefilter weighed 150 grams. Filter B was made to match the same dimensionsof Length, Outside Diameter (OD) and Inside Diameter (ID). Filter Bweighted 112 grams and was formulated with 10% by weight of ATS. Theresulting two filters then featured 27 and 11.2 grams of ATS,respectively. Filter A contained about 2.5 times as much ATS as FilterB. In a test using NSF protocol 53 both filters removed >99% of lead atpH 8.5 and 6.5. The results of this test indicate that the process usedin formulating Filter A was inefficient as compared to Filter B. ATS, ata cost of about $0.025 cents per gram, can be the single most expensiveadditive used in water filtration for the removal of lead and heavymetals. In the above test Filter A required $0.40 US more ATS thanFilter B.

The invention is further illustrated by the following non-limitedapplications. All scientific and technical terms have the meanings asunderstood by one with ordinary skill in the art. The specificapplications which follow illustrate the methods in which the filtrationdevice of the present invention may be utilized and are not to beconstrued as limiting the invention in sphere or scope. The uses may beadapted to variation in order to practice uses embraced by thisinvention but not specifically disclosed. Further, variations of theuses in somewhat different fashion will be evident to one skilled in theart.

Applications

The filtration of gases and liquids is used in a number of industries.The features and benefits disclosed in the present invention provideclear improvements that replace existing technologies. The applicationsherein are meant to exemplify the various aspects of carrying out theinvention and are not intended to limit the invention in any way.

Application 1

Gravity Flow Filtering Devices: Gravity flow for liquid filtrationessentially means that the only force driving a liquid through a filteris the amount of head directly over the filter. The weight of the liquidcreates force. This weight may be increased by increasing the head ordistance between the liquid's highest level and the filter. The headwill gradually diminish as the reservoir of liquid flows out through thefilter. In many applications very little head pressure on the filter canbe generated in portable devices, which are the primary applications forgravity flow filtering. The amount of head is limited to about 70 mmover the filter. The solution to achieve an acceptable flow rate residesin the development of a filter which will indeed flow while stillfiltering out contaminants. For example, for a faster flow rate anoptimum formulation was found to be 25% to 35% PMX CF-1 to about 65% to75% activated carbon granules in the 50 to 150 micron range. The coarsegranules combined with the PMX CF-1 material create an open pore matrixthat flows easily with very minimum head of liquid over the filter. Theactual formulation may be further modified according to the desiredperformance of the filter. For example, a carafe style pitcher usuallyhas only a few inches of head over the filter and therefore must haveexcellent flow through characteristics with very little pressure drop.In the preferred embodiment, a coarse granular activated carbonparticles in the 50 to 150 micron range is blended in a ratio of 70%carbon to 30% PMX CF-1. Factors that affect the flow rate will includethe wall thickness of the filter and the total wetted surface area ofthe filter's exterior.

In other gravity flow devices where there may be more head over thefilter, or where the flow rate need not be fast, and where the challengeis to remove more contaminants, the filter's pore diameter may bereduced through the introduction of the PMX CF-2 material whiledecreasing the median particle distribution size of the compounds oradsorbents, as has been described previously to increase density andreduce median pore diameter. The preferred embodiment for gravity flowdevices starts in a range of from about 30% or more PMX CF-1 to 70%adsorbent/compound blend. This was shown in one experiment where amolded cup shaped filter measuring 10 cm long by 5 cm in diameter wascreated using 30% PMX CF-1 and 70% granular activated carbon in the50–150 micron particle distribution range.

The process used in making a gravity flow filter may be modified wherenecessary to create a more open pore structure, especially where afaster flow rate is desired. After sintering the material in the moldthe filter, preferably a cup-shaped filter, is removed from the mold. Inone experiment using this method and formulation, the cup was filled tothe brim with tap water and allowed to sit. After about 60 seconds thecup began to weep droplets of filtered water along its sides. The bottomof the cup had been made with a slightly thicker wall to discourage theliquid from merely finding the path of least resistance. Over a period10 minutes the cup gradually wetted down as it was re-filledcontinuously. As the cup became fully moistened the flow rate increasedto well above 200 ml per minute. Later experiments discovered that agreater amount of head above the brim of the cup increased liquid flowto 500 ml per minute.

Application 2

Computer disk drives: Anywhere a contaminant removal material is used,performance is improved using the current invention. This advantage wasproven in a test for the removal of an organic vapor. A 1 gram sample ofactivated carbon was placed in a sealed container, where the containerwas filled partially with trimethlpentane (THP), 99% with the loosecarbon placed in an aluminum tray that floated on the surface of thetrimethlpentane. In a second container a molded cube of materialconsisting of activated carbon from the same batch with PMX CF-1 wasused and formulated such that the same amount of activated carbon byweight was contained in the cube. The contents of both trays wereweighed at the commencement of the experiment, then again after 3 hours.The increase in weight of the material in each tray would then determinethe adsorption capability of both the activated carbon in loose form andin molded form. Both trays gained the exact amount of weight in everyexperiment, indicating that the molded form lost no adsorption abilitycompared to the non-molded activated granules. In another experiment,the molded cubes were tested against compressed cubes of the samedimension and general part content with respect to the activated carbon.Here the molded cubes using PMX CF-1 were found to be 200% moreeffective in the adsorption of trimethlpentane.

This breakthrough can be used, in one instance, in computer disk driveswhere activated carbon is used to control humidity and adsorb organicvapors and/or acid gases. The ability to permanently bond carbonparticles to the polyolefin matrix enables the filter cubes or smallsquare, rectangular or circular tabs, or the like, to be manufacturedwithout the shedding of carbon fines while enhancing performance by over200%. Enhanced performance is achieved because the molded part is highlyporous with very little pressure drop. Air that vents the disk drivepasses through the molded carbon part instead of around it. For example,U.S. Pat. No. 6,168,651 teaches a technique of adding projections to acompressed, molded carbon part to expose more surface area to the airthat is directed to flow around and not through the part, since theadsorption takes place on the surface of the part. This demonstrates thelimitations of prior art, and especially the drawbacks inherent to thecompression of filtering materials. Equally important in disk drives isthe regulation of humidity, which activated carbon is able to provide.For example, where the humidity is less than 40 RH, the activated carbonhas no effect on the humidity. However, as the RH increases above 40 theactivated carbon begins to absorb the humidity from the passing airstream, thereby protecting the disk drive from an excess amount ofhumidity, while at the same time allowing for an optimal amount ofhumidity to pass through. The higher the activity of the carbon, ratedby its CTC number, the more moisture it is able to absorb such that thedifference between a CTC number of +65 and +95 can be double in terms ofhumidity regulation. The use of PMX CF-1 and or a blend of PMX CF-1 andPMX CF-2 with activated carbon allow air to flow directly through thefilter matrix rather than around it. This exposes the air stream to allof the carbon, not just the carbon on the surface of the part. Since thetrend in computers is hand held devices the emphasis for filters is tomake them as small as possible. Thus, a 200% increase in performancewill require a filter only one half the size of a compressed carbon partwith binders.

In disk drives, the molded carbon part is positioned between an intakeopening, usually a small pin hole, and a PTFE membrane that is used toprevent particulates from entering the disk drive. In the prior art, theincoming air is drawn over and around the carbon part so as to beexposed to its outer surface. In the current invention, the flow throughcapability of the carbon part may be formulated so that the incoming airwill flow through rather than around the carbon part. This increases theavailable surface area of the carbon to the humidity and undesirablegases in the air used to ventilate the disk drive. Acid gases, forexample, will corrode the head of a disk drive and cause it to fail. Toolittle as well as any excess humidity also can have an adverse affect ondisk drives.

Application 3

Refrigeration: Household refrigerators that dispense chilled drinkingwater and ice use activated carbon water filters to improve the taste,odor and color of tap water. Installed at the point of manufacture, thefilters have in the past typically been of a loose bed activated carbon,since carbon blocks can clog prematurely due to their lack of depthfiltration. Increased filtering, such as the removal of Cryptosporidiumfrom tap water, requires a carbon block or its equivalent which willphysically screen out protozoan parasites. The problem is that thefilter must last a minimum of 6 months to a year without clogging. Wherefilters are used in other applications, the gradual loss of flow rateindicates the filter is clogged. In refrigerators, no such warning isavailable. Thus, it would be preferable to have a filter that screensout protozoan parasites for an extended period of time without the riskof premature clogging of the filter, which would cut off the watersupplying the appliance.

Durability in the filter matrix also translates into a filter thatresists fracturing. One such application is where the filter is used incolder temperatures such as refrigeration. Today most filters areinstalled inside the refrigerator cabinet at eye level for ease ofreplacement and service by the consumer. This is done to encouragefilter replacement on a timelier basis. One potential disadvantage isthat most high performance filters such as carbon blocks are verybrittle and fracture easily. In very cold temperatures where still watermay tend to freeze slightly or ice up, even the slightest stress couldcause the filter to fracture. Filters using the current invention,however, are able to be formulated such that they will actually flexwhen frozen solid. In common refrigerator filter applications, a filterin the preferred embodiment is made using about 50% by weight of PMXCF-1, because of its superior bonding capability with the remainderbeing of compounds and adsorbents to remove common tap watercontaminants such as lead and chlorine. The use of only PMX CF-1material instead of a combination with PMX CF-2 further creates a filterwith excellent depth filtration and minimal pressure drop. Prematureclogging problems are aggravated by flow rates that are very slow, whichis typical in ice maker applications. There is such a slow flow ratethat particulates such as dirt and sediment in the water easily collectand otherwise would obstruct the pores in a filter matrix. The filter ofthe present invention, when used for such appliances, is superiorbecause it will continue to filter at high performance levels withoutclogging and without being effected by freezing temperatures. An idealformulation of materials here would be, by weight, 50% PMX CF-1, 25%powdered activated carbon with a mean particle size of about 22 microns,and 25% granulated activated carbon in the 50 to 150 micron range. Thisformula may be modified to include a lead removal material where needed.In such an instance, the activated carbon is proportionately reduced to40% to accommodate about 10% of a lead removal material such asEngelhard's ATS™. The resulting filter is durable, exhibits excellentdepth filtration and yet has sufficient filtering material to provideconsistent performance.

While the physical characteristics of the filter for refrigerationpurposes have been reviewed above, an equally important improvement isthe increased performance of activated carbon in low temperaturefiltration applications. Activated carbon's ability to adsorb chlorineis increased by higher temperature. In one test, chlorinated tap waterwas passed through a filter of granulated activated carbon in the formof a block matrix. A comparison was evaluated by increasing the watertemperature from 70 degrees F. to 110 degrees F. Notable improvement wasachieved at higher temperatures since chlorine, a gas by nature, becomesincreasingly volatile as the temperature increases. The converse happensat lower temperatures, where activated carbon's ability to removechlorine is diminished as the temperature drops. Since refrigeratorfilters have as a primary objective the removal of chlorine and leadfrom ice and drinking water dispensed from the refrigerator door that isvery cold, the filter's ability to remove chlorine at reduced, coldertemperatures is preferable. Filters made using the preferred embodimentof the current invention provide more available carbon surface area andtherefore have increased capacity, particularly in chlorine removalwhich is wholly dependent on the available surface area of activatedcarbon. As the trend continues for filters to be installed inside therefrigerator cabinet, greater emphasis will be placed on making thefilters smaller and less intrusive. The formulation of the currentinvention has shown to provide excellent performance, especially in theremoval of chlorine and lead while using filters with only half thetotal mass of other filters. This feature combined with the trend toinstall filters inside the refrigerator cabinet instead of outside meanthat the filter will preferably be as small as possible. The currentinvention enables a filter to be formulated to only one half the cubicdimensions of other filters while having more features and benefits.Another feature found to be advantageous in refrigeration is the abilityfor the filter to be molded into panels or shapes other than cylinders,which are a limitation of carbon blocks. Here the filter may be madeinto a flat panel which can fit into less usable space within thecabinet, rather than protrude into usable shelf space. Chlorinated tapwater flows through the panel from one side to the other with thepanel's thickness acting as the filter matrix.

Application 4

Organic Vapor Masks: Organic vapor masks protect the user from inhalingharmful chemical vapors from the air. The prior art involves the use ofa very coarse mesh, granular activated carbon that has been impregnatedwith potassium hydroxide or potassium iodide to enhance the adsorptionof acid gases. The carbon is densely compressed into a canister withperforations on one side for intake of air into the mask. As the airpasses over the coarse granules of activated carbon the adsorption ofthe gases takes place. In the current invention, a porous part is moldedto approximate the same size of the canister in terms of outsidediameter (OD). The part is formed like a shallow cylinder that has acontinuous side wall and a closed end of the same thickness of about 6mm with a radius so that the closed end is rounded. The air flows in aradial direction through the cylinder outside closed end and side wallto the shallow core and into the mask. The formulation of the partinvolves using, in the preferred embodiment, a granular activated carbonwith a particle distribution in the 75 to 150 micron range (60% byweight) to PMX CF-1 (40% by weight). The part is vibrated only slightlyto avoid particle migration and pore size reduction. The ability toreplace the loose bed carbon with a more advanced organic vapor filterin the current invention draws upon the special characteristics thatinclude molding capability of the parts, low pressure drop, and higherperformance. Where granular carbon beds for this application haveparticle distributions in the 500 to 2000 micron range, here theparticles are much finer by comparison and offer greater surface areafor adsorption.

Application 5

Air and Gas Filtration: The principles of causing the surface area ofthe filtering material to be greater while decreasing the pressure dropenhance the filtering performance of gases such as air. Prior artmethods include the creation of flat panels where coarse particles ofactivated carbon are compacted into a given space; alternatively, somefilters designed for air or gas bind fine carbon powders to a fibrousmaterial. The air or gas flows across the fibers and in doing so becomeexposed to the filtering material, which is made of or incorporatesactivated carbon. In the current invention, flat panels may easily bemolded into a geometrical shape that is defined by a length, a width anda thickness. The panel is self supporting and does not require anystructure to contain it. Ease of flow through is achieved by providingcoarse granules of filtering material such as granular activated carbonparticles with PMX CF-1.

Still another application in the filtration of gases is the removal oftoxic organic contaminants from cigarette smoke. Highly activated carbonparticles may be bonded to PMX CF-1 and formed into a filter disk thatis installed in the tar filter. As the smoke passes through thecarbon-polymer matrix any toxic organic vapors are instantly taken upand held on the surface of the carbon particles.

Application 6

Water Filters: The increased demand for high performance in waterfilters is related directly to the continued discovery of residualchemicals, metals and microorganisms found in drinking water and theaccompanying publicity. Contaminants in water may be classified intofour groups: (i) suspended solids; (ii) heavy metals; (iii) organicbased chemicals; such as pesticides and most chemicals; and (iv)micro-organisms. Filters made using the current invention's method ofprocessing and formulations have demonstrated superior performance inthe removal of all four classes of contaminants.

Water filters may be formulated to be durable with excellent density andhaving available a wide range of median pore diameters. The median porediameters may be manipulated by changes in the particle distribution ofthe materials being processed as well as the polymers used to create thefilter matrix. To create the highest performance filter in terms ofremoving the most difficult contaminants, such as VOCs (Volatile OrganicChemicals) a high flow rate filter in one embodiment may be formulatedas follows: It would have 30% by weight of PMX CF-1, 20% by weight ofPMX CF-2 and 50% powdered activated carbon in the range of 20 microns to45 microns. To include the removal of heavy metals, this formula may beadjusted to include about 7% to 15% of a sorbent such as EngelhardMineral's ATS™ zeolites. The exact formula will be determined accordingto the specifications. Conversely, if the filter is to be more open witha lower pressure drop the formula may be adjusted by modifying thepowdered activated carbon (PAC) with a blend of medium coarse carbon inthe 50 micron to 150 micron particle distribution range. The exactamount added depends on part geometry and other factors such as desiredflow rate, pressure drop and depth filtration capability. Typical waterfilter geometry is a cylinder, usually open at both ends or open at oneend only. The cylinder is about 9.5 inches long by 2.25 to 3.0 inches ODwith an inner diameter (ID) of about one inch. Water flows radially fromthe OD to the ID and then out one of the open ends. A typical filter ofthis type will flow at 4 to 6 liters per minute and can be formulated toremove chlorine, pesticides, MTBE (a gasoline additive), VOCs, lindane,asbestos, heavy metals such as lead, and microorganisms such asCryptosporidium. The exact amount is determined by the capacity andperformance requirements placed on the filter. For example, very highflow filters with this geometry and dimensions may require 15% by weightof a lead removal sorbent where performance demands >99% lead reductionat 6 LPM, while at 4 LPM only 10% is needed. In some instances, to meetthe minimum NSF 53 protocol only 7% may be needed.

Another feature of the present invention is the ability to removecontaminants in water through tortuosity rather than absolute micronfiltration. One such difficult contaminant is E. Coli bacteria.Internationally, most countries require a three to four log reduction ofE. coli where the filter makes such a claim. This is accomplished in thecurrent invention in a two step process as follows: the median porediameter is reduced according to the formulation as stated above suchthat even pathogenic bacteria will become trapped inside thelabyrinthine filter matrix. Since pathogenic bacteria will colonizeinside a water filter the trapped microorganisms must be prevented fromreproducing. This growth is called biofilm, which should be prevented.During the preparation and blending of the proposed compounds, a silverimpregnate or silver ion or silver/zinc ion based antimicrobial powderis first blended into the CF-1 and CF-2 polymer. There is anelectrostatic attraction that creates a temporary bond between the twocompounds such that the minute antimicrobial powders, often in themicron diameter range of 0.2 microns to 5.0 microns, cling to thesurface of the PMX particles. In the next step the other materials areblended. During processing, the majority of the fine antimicrobialpowders have been placed where they will immediately form a permanentbond to the structure of the filter. A typical loading onto the filterby weight may be in the range of one percent up to five percent. Aswater passes through the filter matrix the activity of the silver, whichdiffers depending on the particular characteristics of the chosenantimicrobial, deactivates the bacterium's ability to reproduce. Within24 to 48 hours the bacterium dies naturally. Where an ordinary bacteriummay reproduce 40 times per hour in this case there is no reproductionand therefore no biofilm. Dead bacteria decompose into organic matterwhich is instantly adsorbed by the activated carbon powder. There is noodor or residue. This process of eliminating pathogenic bacteria fromwater is unique because it does not require a biocide agent such asiodine or chlorine nor electricity to powder a UV (ultraviolet light)lamp, which are two common methods of removing bacteria.

The use of this method of making a bacteria removal filter relies on theability to properly handle very fine powders (under five microns) andretain their efficacy. Filters whose structural matrix is formed out ofcompressed carbon particles (i.e., carbon blocks) are unable toefficiently conserve such fine powders because a substantial portion ofthese minute particles become lodged in the crevices of the carbonitself such that they wash out of the filter at the first flush, havinghad nothing to permanently bond onto.

The filtering of suspended particles in fluids, particularly liquids, isan essentially preliminary step in filtration. Typically a pre-filter isinstalled first to physically cleanse the liquid of particulates so thatdown stream filters do not become prematurely clogged by fine sedimentparticles. To create a web-like matrix intended to maximize the depthfiltration capabilities of the PMX CF-1, a blend of this polymericmaterial and a flock will capture and hold large quantities of sediment.Flock is a byproduct of textile manufacturing in which remnant threadedmaterial is cut into very small lengths down to only a few microns.These short threads bond easily to the polymer during sintering and thenact as a net to capture particulates. This may be combined with coarseactivated carbon particles to pre-filter both particulates and organics,including chlorine, from water.

In the filtration of water, the present invention should not beconsidered limited to the examples above, but rather should beunderstood to encompass various filter configurations as set out in theclaims. Minor modifications and equivalent techniques will be readilyapparent to those skilled in the art of filter making.

The foregoing description is considered as illustrative only of theprinciples of the invention. The words “comprise,” “comprising,”“include,” “including,” and “includes” when used in this specificationand in the following claims are intended to specify the presence of oneor more stated features, integers, components, or steps, but they do notpreclude the presence or addition of one or more other features,integers, components, steps, or groups thereof. Furthermore, since anumber of modifications and changes will readily occur to those skilledin the art, it is not desired to limit the invention to the exactconstruction and process shown described above. Accordingly, allsuitable modifications and equivalents may be resorted to falling withinthe scope of the invention as defined by the claims which follow.

1. A filter comprising: a plurality of polymer particles, a firstpolymer having an average diameter of about 30 microns to about 40microns and having perforations therein and an irregular, convolutedsurface; a second polymer having a generally non porous sphericalsurface and an average diameter of about 55 microns to about 65 micronsand activated carbon, the activated carbon being sized from sub-micronto about 1000 microns, the activated carbon comprising from about 35% to90% by weight of the finished filter, the first polymer comprising fromabout 10% to about 65% by weight of the finished filter and the secondpolymer comprising from about 0.5% to about 65% by weight of thefinished filter.
 2. The filter of claim 1, wherein the filter furthercomprises: a lead removal compound operatively associated with theplurality of polymer particles and the activated carbon.
 3. The filterof claim 1, wherein the filter further comprises: an antimicrobialcompound operatively associated with the plurality of polymer particlesand the activated carbon.
 4. The filter of claim 3, wherein theantimicrobial further comprises: ions that discourage bacterial growth.5. The filter of claim 4, wherein the ions are silver.
 6. The filter ofclaim 4, wherein the ions are zinc.
 7. The filter of claim 4, whereinthe ions are halogenide.
 8. The filter of claim 1, wherein the filterhas any geometric shape.
 9. The filter of claim 8, wherein the geometricshape is in the form of a flat panel.